javaAPI文档用什么打开 javafxapi文档

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技术领航员 2023-09-23 11:52:32

文章标签 javaAPI文档用什么打开 java javafx 图形多媒体 文章分类 Java 后端开发

这个章节介绍Image Ops，这个API可以使你在你的javaFX应用中读写像素。你将会学到如果从图片中读取像素和写像素到图片中或者创建

一个快照。

Image Ops API概述

Image Ops API 由下面的类和接口组成，这些类在javafx.scene.image包中

Image：代表了一个图片，这个类提供了一个PixelReader类，这个类可以直接从图片中读取像素
WritableImage：Image的子类，提供了PixelWriter类，这个类可以写像素到图片中。会创建一个空的WritableImage，直到你写
素到这个对象中。
PrixelReader：这是一个接口，定义了读取像素的方法。
PixelWriter：这是一个接口，定义了向WritableImage对象中写像素的方法。
PixelFormat：为格式化的像素数据定义了布局。
WritablePixelFormat:PixelFormat的子类，代表了可存储所有颜色的像素格式。它可以当做向任意图片写像素的目标格式。

下面我们用实例介绍这个API的使用

从图片读像素

你可能对javafx.scene.image.Image类已经熟悉了，它可以使你在javaFX应用中操作图片，下面的例子想我们展示了如何加载oracle.com

网址中的JavaF图标并把这个图标加入到javaFX场景图中。代码如下：

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
 
public class ImageOpsTest extends Application {
    
    @Override
    public void start(Stage primaryStage) {
     
        // Create Image and ImageView objects
        Image image = new Image("http://docs.oracle.com/javafx/"
        + "javafx/images/javafx-documentation.png");
        ImageView imageView = new ImageView();
        imageView.setImage(image);
      
        // Display image on screen
        StackPane root = new StackPane();
        root.getChildren().add(imageView);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setTitle("Image Read Test");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
 
    public static void main(String[] args) {
        launch(args);
    }
}

运行项目，如下图所示：

javaAPI文档用什么打开 javafxapi文档_图形

下面我们修改代码，从像素中读取颜色。我们可以调用getPixelReader()方法，或者使用getColor(x,y)方法。会返回一个PixelReader对

象，我们可以利用这个对象来获取指定坐标的像素颜色。代码如下：

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.image.PixelReader;
import javafx.scene.paint.Color;
 
public class ImageOpsTest extends Application {
    
    @Override
    public void start(Stage primaryStage) {
     
        // Create Image and ImageView objects
        Image image = new Image("http://docs.oracle.com/javafx/"
        + "javafx/images/javafx-documentation.png");
        ImageView imageView = new ImageView();
        imageView.setImage(image);
       
        // Obtain PixelReader
        PixelReader pixelReader = image.getPixelReader();
        System.out.println("Image Width: "+image.getWidth());
        System.out.println("Image Height: "+image.getHeight());
        System.out.println("Pixel Format: "+pixelReader.getPixelFormat());
        
        // Determine the color of each pixel in the image
        for (int readY = 0; readY < image.getHeight(); readY++) {
            for (int readX = 0; readX < image.getWidth(); readX++) {
                Color color = pixelReader.getColor(readX, readY);
                System.out.println("\nPixel color at coordinates ("
                        + readX + "," + readY + ") "
                        + color.toString());
                System.out.println("R = " + color.getRed());
                System.out.println("G = " + color.getGreen());
                System.out.println("B = " + color.getBlue());
                System.out.println("Opacity = " + color.getOpacity());
                System.out.println("Saturation = " + color.getSaturation());
            }
        }
           
        // Display image on screen
        StackPane root = new StackPane();
        root.getChildren().add(imageView);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setTitle("Image Read Test");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
 
    public static void main(String[] args) {
        launch(args);
    }
}

这段代码直接用一个循环读取了图片上所有坐标位置的像素颜色。输出部分如下：

... // beginning of output omitted

Pixel color at coordinates (117,27) 0x95a7b4ff

R = 0.5843137502670288

G = 0.6549019813537598

B = 0.7058823704719543

Opacity = 1.0

Saturation = 0.17222220767979304

Pixel color at coordinates (118,27) 0x2d5169ff

R = 0.1764705926179886

G = 0.3176470696926117

B = 0.4117647111415863

Opacity = 1.0

Saturation = 0.5714285662587809

... // remainder of output omitted

你可能想改变像素的颜色并且把这些改变显示到屏幕上，想想一下，图片对象是只读的，你要是想写新数据，你需要一个WritebleImage

实例。

写像素到图片：

下面我们修改上面的例子。代码如下：

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.image.PixelReader;
import javafx.scene.image.PixelWriter;
import javafx.scene.paint.Color;
import javafx.scene.image.WritableImage;
 
public class ImageOpsTest extends Application {
    
    @Override
    public void start(Stage primaryStage) {
     
        // Create Image and ImageView objects
        Image image = new Image("http://docs.oracle.com/javafx/"
        + "javafx/images/javafx-documentation.png");
        ImageView imageView = new ImageView();
        imageView.setImage(image);
       
        // Obtain PixelReader
        PixelReader pixelReader = image.getPixelReader();
        System.out.println("Image Width: "+image.getWidth());
        System.out.println("Image Height: "+image.getHeight());
        System.out.println("Pixel Format: "+pixelReader.getPixelFormat());
        
        // Create WritableImage
         WritableImage wImage = new WritableImage(
                 (int)image.getWidth(),
                 (int)image.getHeight());
         PixelWriter pixelWriter = wImage.getPixelWriter();
       
        // Determine the color of each pixel in a specified row
        for(int readY=0;readY<image.getHeight();readY++){
            for(int readX=0; readX<image.getWidth();readX++){
                Color color = pixelReader.getColor(readX,readY);
                System.out.println("\nPixel color at coordinates ("+
                        readX+","+readY+") "
                        +color.toString());
                System.out.println("R = "+color.getRed());
                System.out.println("G = "+color.getGreen());
                System.out.println("B = "+color.getBlue());
                System.out.println("Opacity = "+color.getOpacity());
                System.out.println("Saturation = "+color.getSaturation());
                
                // Now write a brighter color to the PixelWriter.
                color = color.brighter();
                pixelWriter.setColor(readX,readY,color);
            }
        }
        
        // Display image on screen
        imageView.setImage(wImage);
        StackPane root = new StackPane();
        root.getChildren().add(imageView);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setTitle("Image Write Test");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
 
    public static void main(String[] args) {
        launch(args);
    }
}

这个例子创建了一个WritableImage，这个对象和之前的Iamge对象的宽高是一样的。然后获得一个PixelWriter对象，这个对象负责写信的

像素数据到新的图片。通过brighter()方法获得一个更明亮的像素颜色，然后调用pixelWriter.setColor方法为新图片添加新数据。执行

代码显示如下，我们可以看到这个图片比之前的更明亮些：

javaAPI文档用什么打开 javafxapi文档_java_02

使用字节数组和PixelFormats

之前的例子已经成功的获得和修改了像素的颜色，这个例子使用PixelFormat来指定像素数据写入的方法。使用Canvas代替了ImageView.

import java.nio.ByteBuffer;
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.effect.DropShadow;
import javafx.scene.image.PixelFormat;
import javafx.scene.image.PixelWriter;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
 
public class ImageOpsTest extends Application {
 
    // Image Data
    private static final int IMAGE_WIDTH = 10;
    private static final int IMAGE_HEIGHT = 10;
    private byte imageData[] = 
        new byte[IMAGE_WIDTH * IMAGE_HEIGHT * 3];
    
    // Drawing Surface (Canvas)
    private GraphicsContext gc;
    private Canvas canvas;
    private Group root;
 
    public static void main(String[] args) {
        launch(args);
    }
 
    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("PixelWriter Test");
        root = new Group();
        canvas = new Canvas(200, 200);
        canvas.setTranslateX(100);
        canvas.setTranslateY(100);
        gc = canvas.getGraphicsContext2D();
        createImageData();
        drawImageData();
        primaryStage.setScene(new Scene(root, 400, 400));
        primaryStage.show();
 
    }
 
    private void createImageData() {
        int i = 0;
        for (int y = 0; y < IMAGE_HEIGHT; y++) {
            int r = y * 255 / IMAGE_HEIGHT;
            for (int x = 0; x < IMAGE_WIDTH; x++) {
                int g = x * 255 / IMAGE_WIDTH;
                imageData[i] = (byte) r;
                imageData[i + 1] = (byte) g;
                i += 3;
            }
        }
    }
 
    private void drawImageData() {
        boolean on = true;
        PixelWriter pixelWriter = gc.getPixelWriter();
        PixelFormat<ByteBuffer> pixelFormat = PixelFormat.getByteRgbInstance();
        for (int y = 50; y < 150; y += IMAGE_HEIGHT) {
            for (int x = 50; x < 150; x += IMAGE_WIDTH) {
                if (on) {
                    pixelWriter.setPixels(x, y, IMAGE_WIDTH,
                            IMAGE_HEIGHT, pixelFormat, imageData, 
                            0, IMAGE_WIDTH * 3);
                }
                on = !on;
            }
            on = !on;
        }
 
        // Add drop shadow effect
        gc.applyEffect(new DropShadow(20, 20, 20, Color.GRAY));
        root.getChildren().add(canvas);
    }
}

运行如下图所示：

javaAPI文档用什么打开 javafxapi文档_javaAPI文档用什么打开_03

创建一个快照

javafx.scene.Scene类提供了一个快照的方法，该方法返回WritableImage。当使用java的IamageIO类的时候，我们可以在文件系统中存储

一个快照。代码如下：

import java.io.File;
import java.io.IOException;
import java.nio.ByteBuffer;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.canvas.GraphicsContext;
import javafx.scene.effect.DropShadow;
import javafx.scene.image.PixelFormat;
import javafx.scene.image.PixelWriter;
import javafx.scene.image.WritableImage;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javax.imageio.ImageIO;
 
public class ImageOpsTest extends Application {
 
    // Image Data
    private static final int IMAGE_WIDTH = 10;
    private static final int IMAGE_HEIGHT = 10;
    private byte imageData[] = new byte[IMAGE_WIDTH * IMAGE_HEIGHT * 3];
    // Drawing Surface (Canvas)
    private GraphicsContext gc;
    private Canvas canvas;
    private Group root;
 
    public static void main(String[] args) {
        launch(args);
    }
 
    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("PixelWriter Test");
        root = new Group();
        canvas = new Canvas(200, 200);
        canvas.setTranslateX(100);
        canvas.setTranslateY(100);
        gc = canvas.getGraphicsContext2D();
        createImageData();
        drawImageData();
 
        Scene scene = new Scene(root, 400, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
 
        //Take snapshot of the scene
        WritableImage writableImage = scene.snapshot(null);
 
        // Write snapshot to file system as a .png image
        File outFile = new File("imageops-snapshot.png");
        try {
            ImageIO.write(SwingFXUtils.fromFXImage(writableImage, null),
                    "png", outFile);
        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }
    }
 
    private void createImageData() {
        int i = 0;
        for (int y = 0; y < IMAGE_HEIGHT; y++) {
            System.out.println("y: " + y);
            int r = y * 255 / IMAGE_HEIGHT;
            for (int x = 0; x < IMAGE_WIDTH; x++) {
                System.out.println("\tx: " + x);
                int g = x * 255 / IMAGE_WIDTH;
                imageData[i] = (byte) r;
                imageData[i + 1] = (byte) g;
                System.out.println("\t\tR: " + (byte) r);
                System.out.println("\t\tG: " + (byte) g);
                i += 3;
            }
        }
        System.out.println("imageData.lengthdrawImageData: " + imageData.length);
    }
 
    private void drawImageData() {
        boolean on = true;
        PixelWriter pixelWriter = gc.getPixelWriter();
        PixelFormat<ByteBuffer> pixelFormat = PixelFormat.getByteRgbInstance();
        for (int y = 50; y < 150; y += IMAGE_HEIGHT) {
            for (int x = 50; x < 150; x += IMAGE_WIDTH) {
                if (on) {
                    pixelWriter.setPixels(x, y, IMAGE_WIDTH,
                    IMAGE_HEIGHT, pixelFormat, 
                    imageData, 0, IMAGE_WIDTH * 3);
                }
                on = !on;
            }
            on = !on;
        }
 
        // Add drop shadow effect
        gc.applyEffect(new DropShadow(20, 20, 20, Color.GRAY));
        root.getChildren().add(canvas);
    }
}

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